Signal processing apparatus used for optical signal output device and optical displacement detection system

Abstract

A signal processing apparatus includes a first signal processing unit and a second signal processing unit. The first signal processing unit executes a first predetermined operation with respect to first and second signal groups and to extract a first component having a predetermined characteristic when an optical signal output device is in a normal state, the first signal group whose amplitude or direct current component gradually increases with a predetermined direction displacement of a displacement detection target, the second signal group whose amplitude or direct current component gradually decreases with the predetermined direction displacement of the displacement detection target. The second signal processing unit executes a second predetermined operation with respect to the first and second signal groups and to extract an output containing a second component, which is peculiar to an optional position of the displacement detection target.

What is claimed is: 
     
       1. A signal processing apparatus used for an optical signal output device, comprising:
 a first signal processing unit configured to execute a first predetermined operation with respect to first and second signal groups and to extract a first component having a predetermined characteristic when an optical signal output device is in a normal state, the first signal group, which is output from the optical signal output device connected to a displacement detection target and whose amplitude or direct current component gradually increases with a predetermined direction displacement of the displacement detection target, the second signal group, which is output from the optical signal output device and whose amplitude or direct current component gradually decreases with the predetermined direction displacement of the displacement detection target; and 
 a second signal processing unit configured to execute a second predetermined operation with respect to the first and second signal groups and to extract an output containing a second component, which is peculiar to an optional position of the displacement detection target. 
 
     
     
       2. The apparatus according to  claim 1 , further comprising:
 a notification unit configured to compare a first component actually extracted by the first signal processing unit with the predetermined characteristic to determine whether or not there is a difference between the first component and the predetermined characteristic, and to notify whether or not the optical signal output device is in a normal state in accordance with the compared result, or to notify a degree of the difference between the first component actually extracted by the first signal processing unit and the predetermined characteristic in accordance with the compared result. 
 
     
     
       3. The apparatus according to  claim 1 , wherein the first signal processing unit calculates the sum of an amplitude of the first signal group and an amplitude of the second signal group, or the sum of a direct current component of the first signal group and a direct current component of the second signal group, as the first predetermined operation. 
     
     
       4. The apparatus according to  claim 1 , wherein the optical signal output device comprises:
 a scale, which is formed of first and second track patterns configured so that a direction parallel to a displacement direction of the displacement detection target is set as a longitudinal direction; 
 a light source configured to irradiate a light beam to the scale; and 
 a sensor head, which includes: a first photodetector detecting a light beam irradiated from the light source by means of the first track pattern to generate the first signal group; and a second photodetector detecting a light beam irradiated from the light source by means of the second track pattern to generate the second signal group, 
 the first track pattern, the second track pattern, the first photodetector, the second photodetector and the light source being arranged so that detection by the first photodetector is associated with detection of the second photodetector. 
 
     
     
       5. The apparatus according to  claim 4 , wherein the first track pattern, the second track pattern, the first photodetector, the second photodetector and the light source are arranged so that the first component extracted by the first signal processing unit becomes approximately constant without depending on a displacement in a predetermined section of the displacement detection target. 
     
     
       6. An optical displacement detection system comprising:
 an optical signal output device comprising: 
 (1) a scale, which is formed of first and second track patterns configured so that a direction parallel to a displacement direction of a displacement detection target is set as a longitudinal direction; 
 (2) a light source configured to irradiate a light beam to the scale; and 
 (3) a sensor head, which includes: a first photodetector detecting a light beam irradiated from the light source by means of the first track pattern to generate a first signal group in which an amplitude or direct current component gradually increases with a displacement of a predetermined direction of the displacement detection target; and a second photodetector detecting a light beam irradiated from the light source by means of the second track pattern to generate a second signal group in which an amplitude or direct current component gradually decreases with the displacement of the predetermined direction of the displacement detection target, the first track pattern, the second track pattern, the first photodetector, the second photodetector and the light source being arranged so that detection by the first photodetector is associated with detection of the second photodetector, and 
 a signal processing apparatus comprising: 
 (1) a first signal processing unit configured to execute a first predetermined operation with respect to the first and second signal groups and to extract a first component having a predetermined characteristic when the optical signal output device is in a normal state; and 
 (2) a second signal processing unit configured to execute a second predetermined operation with respect to the first and second signal groups and to extract an output containing a second component, which is peculiar to an optional position of the displacement detection target, as a displacement of the displacement detection target. 
 
     
     
       7. The system according to  claim 6 , wherein the signal processing apparatus further comprises a notification unit configured to compare a first component actually extracted by the first signal processing unit with the predetermined characteristic to determine whether or not there is a difference between the first component and the predetermined characteristic, and to notify whether or not the optical signal output device is in a normal state in accordance with the compared result, or to notify a degree of the difference between the first component actually extracted by the first signal processing unit and the predetermined characteristic in accordance with the compared result. 
     
     
       8. The system according to  claim 6 , wherein the first signal processing unit calculates the sum of an amplitude of the first signal group and an amplitude of the second signal group, or the sum of a direct current component of the first signal group and a direct current component of the second signal group, as the first predetermined operation. 
     
     
       9. The system according to  claim 6 , wherein the first track pattern, the second track pattern, the first photodetector, the second photodetector and the light source are arranged so that the first component extracted by the first signal processing unit becomes approximately constant without depending on a displacement in a predetermined section of the displacement detection target. 
     
     
       10. The system according to  claim 6 , wherein the first and second track patterns are formed with a gray track formed of any of:
 a grayscale pattern, which is an optical pattern such that any of an effective reflectance, an effective transmittance and a diffraction efficiency gradually increases or decreases in a predetermined section along a displacement direction of the displacement detection target; and 
 a modulation code pattern, which is a pattern having an optical characteristic such that the grayscale pattern and an encode pattern are combined, the encode pattern being an optical pattern such that any of an effective reflectance, an effective transmittance and a diffraction efficiency changes at a predetermined spatial period with respect to a direction along a displacement direction of the displacement detection target. 
 
     
     
       11. The system according to  claim 10 , wherein the first and second track patterns are formed with at least the modulation code pattern, and
 the scale and the sensor head are arranged so that when a light beam irradiated from the light source is transmitted, reflected or diffracted by the modulation code pattern, a diffraction pattern having a spatial period pi is formed on light-receiving surfaces of the first and second photodetectors, and 
 a plurality of light-receiving element arrays, which has a spatial period same as the diffraction pattern of the spatial period pi or integer multiples of the spatial period, is arranged on light-receiving surfaces of the first and second photodetectors in a state of being shifted with respect to a direction along a displacement direction of the displacement detection target to detect the diffraction pattern at a mutually different spatial phase difference, and further 
 the signal processing apparatus further includes: 
 a plurality of channel in-phase adder unit configured to add outputs from the light-receiving element arrays receiving an in-phase component of the diffraction pattern of a plurality of light-receiving element arrays of first and second photodetectors; and 
 a relative displacement operation unit configured to calculate the displacement in combination with a plurality of channel outputs output from the in-phase adder unit.